City Grapples with Rising Seas

Climate change is causing global sea levels to rise as melting glaciers and ice sheets turns frost into water that drains into oceans, while warming sea water expands ocean volume. Along California’s coastline, where nearly 70 percent of the state’s residents live, swelling seas are more frequently colliding with extreme storms, resulting in drowned beaches, flooded homes and businesses, damaged roads and public infrastructure.

Over the past century, sea levels increased by about eight inches in San Francisco, according to The Office of Environmental Health Hazard Assessment (OEHHA). OEHHA points to accelerating loss of ice from Greenland and Antarctica as especially concerning. It worries that potential sea level rise from continued melting and ice sheet collapse could be catastrophic for coastal communities.

Sarah Atkinson, Hazard Resilience Senior Policy Manager at SPUR, a nonprofit public policy organization based in San Francisco, researches the hazards of sea level and groundwater rise, flooding, and earthquakes. She said the City could experience heightened sea levels of between three and six feet by 2100 based on California Ocean Protection Council data. Some areas, such as Mission Bay and India Basin, will be more vulnerable due to their ecological history – former marshlands – historical land uses, previous infrastructure investments, and community demographics. 

Mission Bay was previously known as San Francisco Bay marshlands. From the 1800s to early 1900s, the area was filled in and used for industrial activities.

“Today, this area is one of the City’s densest residential areas exposed to sea level rise. New mixed-use developments have increased commercial activities, job access, and affordable housing in the neighborhood,” said Aktinson. “Although there have been significant investments into raising the shoreline, parts of the inland area are at sea level, making them vulnerable to inland flooding from major storms, groundwater rise, and coastal flooding entering at unprotected low-elevation locations along the shoreline. Sea level rise will also expose Mission Bay’s buried industrial history as contaminants rise to the surface, impacting both human and ecological health.” 

In the 2010s, SPUR led an extensive process to develop the Ocean Beach Master Plan, a comprehensive vision to address sea level rise, protect infrastructure, restore coastal ecosystems and improve public access. 

“Planning for major infrastructure projects takes many years,” said Aktinson. 

According to Brad Benson, Waterfront Resilience Program Director at the Port of San Francisco, which manages 7.5 miles of waterfront stretching from Pier 98 to Fisherman’s Wharf, there’s a need to adapt shoreline elevations to defend against future sea level rise.

“The Port of San Francisco is a substantial piece of our City’s waterfront and home to some of the most beloved landmarks, public attractions, and open spaces,” said Benson. “The waterfront is also integral to our City’s economic activity, transportation networks like BART and Muni, critical drinking water and wastewater utilities, and disaster response facilities. What happens along the San Francisco Waterfront will impact San Franciscans in every corner of the City.” 

The Port, in collaboration with the U.S. Army Corps of Engineers (USACE), is conducting a waterfront flood study, one of several coordinated resiliency activities being undertaken in partnership with federal, state, and local agencies to plan for anticipated seismic activity, flooding, and sea level rise. Earlier this year, the Port and USACE released a Draft Plan, which identifies the study’s long-term vision and establishes goals and policies to achieve it. 

“Reflecting more than six years of community engagement and public input, the Draft Plan proposes to defend the shoreline within the Port’s jurisdiction against sea level rise. It indicates approximately where to build coastal flood defenses and how much sea level rise future coastal flood defenses will manage before they need to be adapted to higher water levels,” said Benson. “It includes a monitoring and adaptation plan to track evidence of sea level rise and global climate change to understand when future actions will be required.” 

According to Benson, the proposed measures are estimated to cost $13.5 billion. If approved by the U.S. Congress, the federal government may pay up to 65 percent of the costs.

“The Port will continue to seek public input on the effort to defend the waterfront against sea level rise and coastal flooding,” said Benson. 

“Funding needs may require the City to take out bonds or create special tax districts for adaptation projects. It will be important for the City to design these future funding efforts with vulnerable residents in mind, to avoid cost burdens and/or displacement for low-income residents,” said Aktinson. “It will also be important for residents to support these financing efforts and understand the benefits of investing in sea level rise mitigation and adaptation measures now to save money later.”

Under Proposition K, on the November ballot, a mile-long portion of the Great Highway would close to car traffic permanently by 2026, as part of a project to protect the City’s western shore from rising sea levels. Proposition 4, also to be voted on next month, would create a $10 billion state bond that includes $350 million for flood management projects along California’s urban shorelines, such as the San Francisco waterfront. 

“SPUR recommends a yes vote for Prop 4,” said Aktinson.